Nitrile-metal carbonyl complexes



Unitcd States Patent Ofifice 3,065,250 Patented Nov. 20, 1962 Thepresent invention relates to new and useful nitrilemetal carbonylcomplexes and to the method of their preparation. More specifically, theinvention relates to nitrile-metal carbonyl complexes where the metal isa group VI-B metal (chromium, molybdenum or tungsten) according to theperiodic system (see Langes Handbook of Chemistry, eighth edition, pages5657, 1952).

Some hydrogen cyanide-metal carbonyl complexes have been reported.However, complexes of hydrogen cyanide and a group VI-B metal carbonylhave never been reported, and attempts to prepare them have beenunsuccessful. The present invention is based on the unforeseen discoverythat nitriles undergo a general reaction with group Vl-B metal carbonylsto form new and useful nitrile-metal carbonyl complexes, which resultfrom the replacement of one or more carbonyl groups of the metalcarbonyl by the nitrile.

More particularly, the present invention relates to crystalline, yellowto orange complexes of a nitrile and a group VLB metal carbonyl, saidcomplexes having the general formula in which R is a hydrocarbon radicalor a hydrocarbon radical containing as a substituent a nucleophilicgroup, i.e., a group that increases the electron availability in thetriple bond region of the nitrile group, M is a hexacoordinated atom ofa metal of group V-I-B of the periodic table, x is an integer from 1 to2 inclusive, n is an integer from 1 to 3 inclusive, y is an integer from2 to 5 inclusive and z is an integer from 1 to 2 inclusive, and to themethod of preparing such complexes which comprises either (1) reacting agroup VI-B metal carbonyl [M(CO) with a nitrile having the formula R(CN)where R and x are as above defined, under conditions where carbonmonoxide is removed as it is formed or (2) reacting a preformednitrile-metal carbonyl complex having the general formula in which M, x,n, y and z are as above defined and R is a hydrocarbon radical or ahydrocarbon radical containing as a substituent a nucleophilic group,with a nitrile having the formula R(CN) where R and x are as abovedefined, thereby replacing the nitrile component of the complex withanother nitrile component.

Before describing the invention in greater detail, the followingexamples are presented for purpose of illustration, parts andpercentages being by weight unless otherwise specified.

EXAMPLE 1 A reaction vessel fitted with a condenser and means to measurethe amount of carbon monoxide evolved was charged with 5.2 parts ofmolbdenum carbonyl and flushed with nitrogen. Then 78.3 parts of dryacetonitrile were added and the reaction mixture refluxed at atemperature of 8081 C. for 3 hours, carbon monoxide being evolved thewhole time, approximately 3 moles of carbon monoxide being evolved permole of molybdenum carbonyl. The solution became yellow soon after themixture began to reflux and all of the molybdenum carbonyl dissolved.After removing the excess acetonitrile under vacuum at room temperature,there remained 5.8 parts of a yellow crystalline solid which was veryunstable in air, becoming brown immediately upon contact with air.

A sample of the product was analyzed under an inert atmosphere forpercent carbon, hydrogen, nitrogen and molybdenum. The results of theanalysis compared with the theoretical percentages for (CH CN) Mo(CO)are tabulated below.

The product was identified as (CH3CN)3MO(CO)3 which is in agreement withthe evolution of three moles of carbon monoxide per mole of molybdenumcarbonyl.

The product was insoluble in benzene, carbon tetrachloride, and water;somewhat soluble in methanol; and soluble in acetonitrile, ethyleneglycol dimethyl ether, tetrahydrofuran and dimethylformamide.

The infrared spectra of the product was obtained and found to be greatlydifferent from the spectra of M0(CO) In both cases the determinationswere made in acetonitrile.

It was found that when the exact same reaction was attempted underidentical conditions in a sealed reaction vessel, thereby preventing therelease of carbon monoxide, the acetonitrile and molybdenum carbonylremained unchanged.

EXAMPLE 2 This example shows that the reaction between the metalcarbonyl and nitrile is an equilibrium reaction and can be readilyreversed by a small partial pressure of carbon monoxide.

A sample of an acetonitrile-molybdenum carbonyl complex (described inExample 1) in cyclohexane solution was placed in a stainless steelautoclave in the absence of air. The autoclave was flushed with carbonmonoxide, and the complex was allowed to react at 3000 p.s.i.g'. carbonmonoxide pressure at a temperature of C. for 6 hours. On coolingmolybdenum carbonyl and acetonitrile were recovered.

EXAMPLE 3 (CH CN) Mo(CO) The results of an elementary analysis aretabulated below.

I Found I Theory Percent O 37. 78 35. 66 Percent H 2. 98 3.0 Percent N13.02 13. 92

EXAMPLE 4:

A reaction was conducted as in 'Example 1 using 5.2 parts of molybdenumcarbonyl, 7.8 parts of acetonitrile and 39.6 parts of methanol asdiluent. The reaction mixture was refluxed for 5 hours at a temperatureof 65 C. with evolution of carbon monoxide. A light yellow solu- 3 tionresulted, and after evaporation of the solvent under vacuum, a yellowcrystalline solid, identical to the complex described in Example 1, wasobtained.

EXAMPLE 5 A reaction vessel fitted with a condenser and means to measurethe amount of carbon monoxide evolved was charged with 15.6 parts ofmolybdenum carbonyl and flushed with nitrogen. Then 30 parts ofbenzonitr-ile in 68.4 parts of n-heptane were added and the reactionmixture refluxed at a temperature of 101-102 C. for 14 hours. Carbonmonoxide equivalent to 3.06 moles per mole of molybdenum carbonyl wasevolved. During the reaction a yellow crystalline solid precipitated andwas isolated by filtration in the absence of air. The product wasidentified as (C H CN) Mo(CO) The results of an elementary analysis wereas follows:

EXAMPLE 6 Molybdenum carbonyl (5.2 parts) was charged to a reactionvessel as described in Example 1. Then 9.5 parts of adiponitriledissolved in 68.4 parts of heptane were added and the reaction mixturerefluxed at a temperature of l0il-10 l C. for about 23 hours. Duringthis time, an amount of carbon monoxide equivalent to 3.1 moles per moleof molybdenum carbonyl was evolved. The reaction mixture separated intotwo phases during the reaction, the lower phase of which crystallized oncooling. A yellow crystalline product was removed by filtration in theabsence of air. The product was identified as [NC(CH )4CN] Mo(CO) Theresults of an elementary analysis were as follows:

Found Theory Percent 0.- 50. 87 50. 00 Percent 11.. 4. 63 4. 79 PercentN- 17.93 16. 66

EXAMPLE 7 A reaction was conducted exactly as in Example 6 except theamount of adiponitrile reactant was reduced to 3.2 parts. Carbonmonoxide evolution ceased after 11 hours and a light yellow crystallinesolid was isolated EXAMPLE "8 A reaction was conducted as in Example 1using 5.2 parts of molybdenum carbonyl, 7.8 parts of propionitrile and68.4 parts of heptane reaction medium. After refluxing at a temperatureof 88-90 C. for 9 hours, the evolution of carbon monoxide became veryslow and the reaction was stopped. The total carbon monoxide evolvedamounted to approximately two moles per mole of molybdenum carbonyl. Thereaction mixture consisted of two liquid phases. On cooling the lowerphase crystallized and a light yellow crystalline solid was isolated byfiltration in the absence of air. The product was identified 4 as (CH CHCN) Mo(CO) The tary analysis were as follows:

results of an elemen- Found Theory Percent C Percent 11.. Percent NPercent Mo EXAMPLE 9* In another experiment conducted in the same manneras Example 8, 15 parts of n-capronitrile was substituted for thepropionitrile. Refluxing was conducted at a tem perature of 101 C. Abrownish yellow crystalline prodnot was obtained and exhibited aninfrared spectra typical of a nitrile-molybdenurn carbonyl complex.

EXAMPLE 10 (CH C H CN) M0(CO) The results of an elementary analysis wereas follows:

Found Theory Percent C Percent N Percent Mo EXAMPLE 11 A reaction wasconducted as in Example 1 using 5.2 parts of molybdenum carbonyl, 8.0parts of acrylonitrile and 68.4 parts of heptane as the reaction medium.After refluxing at a temperature of 100 C. for 14 hours, the evolutionof carbon monoxide practically ceased and the reaction was stopped.During this time the reaction medium became yellow in color and anorange crystalline solid precipitated. This crystalline solid wasrecovered by filtration in the absence of air. Infrared analysis of asample of the crystalline solid failed to disclose the presence ofunsaturation. Another sample was analyzed for percentage carbon,hydrogen, nitrogen and molybdenum. The results of the analysis comparedwith the theoretical percentages for (CH :CHCN)2MO'(C0)2 are tabulatedbelow:

Found Theory Percent C 39. 59 37. 27 Percent H... 2. 2. 34 Percent N 10.51 10. 86 Percent Mo 34. 44 37- 17 While the exact structure of thiscomplex is unknown, the following structure is probable.

1120 N N CH:

EXAIWPLES 12-21 P 5 mole of metal carbonyl used and the calculatednumber remained dissolved throughout the hydrogenation reof carbonylgroups replaced are given in Table I. action.

TABLE I Moles Number Parts Parts Parts Reae- Reae- C0 of car- Ex. Metalcarof car- Nitrile of Diluent of diltiou tiou evolved] bonyl Color ofcrystal- No. bonyl bonyl nitrile uent time, temp, mole cargroups linecomplex hr. C bonyl replaced used 12 OM00...- 2.2 Aeeto 25.5 82 3.0 3Light yellow. 13 W(CO)s 3. do 21. 5 84-85 2.6 3 Grcenish-yellow.

5.2 lsobutyro 7 104 2. 4 2 Y w. 5. 2 Succino. 12 101-102 2. 7 3Grcenish-yellow. 5. 2 Belize.. 7 100 0.5 1 Deep yellow. 5. 2 3-butene12. 5 90-95 3. 9 4 Yellow. 5. 2 p-Ohloroben 10.0 102 2. 18 2 Brilliantyellow. Mo (C On. 5. 2 Oyanoacetamide. l0. 5 99 1. 9 2 Yellow. 20 Mo(CO)w 5.2 Ethylcyanoacetatnide..- 12.0 105 2. 5 3 D0. 21 Mo(CO) 5.2p-Methoxybenzo 12 100 2.9 3 Light yellow.

EXAMPLES 2224 Three preparations were run in which nitrile-molybdenumcarbonyl complexes were prepared by the displacement of acetonitrilewith another nitrile. In each run a solution of acetonitrile-molybdenumcarbonyl complex was prepared from 5.2 parts of molybdenum carbonyl and78.3 parts of acetonitrile exactly as described in Example 1.

Example 22.Benzonitrile (10 parts) was added to the first solutioncontaining the acetonitrile complex at a temperature of 80-8l C. Theexcess acetonitrile was removed under vacuum leaving a yellowcrystalline solid which was identical with the crystalline solidprepared in Example 5.

Example 23.-n-Capronitrile (6 parts) was added to the second solutioncontaining the acetonitrile complex at a temperature of 7980 C. Theexcess acetonitrile was removed under vacuum leaving a crystallineproduct identical to the product of Example 9.

Example 24.-Malononitrile (4 parts) was added to the third solutioncontaining the acetonitrile complex at a temperature of 8082 C. Theexcess acetonitrile was removed under vacuum leaving a crystallinesolid. Infrared analysis revealed that the solid was amalononitrile-molybdenum carbonyl complex.

EXAMPLE 25 This example shows the use of a complex of this invention asa catalyst in the hydrogenation of a nitrile.

An autoclave was charged to one half its volume with acetonitrile andflushed with nitrogen. Then an amount of (CH CN) M0(CO) (theacetonitrile-molybdenum carbonyl complex described in Example 1)equivalent to 7.5% by weight of the total reaction mixture was addedunder nitrogen atmosphere. The complex catalyst immediately went intosolution. Next, the auto clave was evacuated and pressured to 4000 psi.with hydrogen. After 4 hours at a temperature of 200 C., the reactionwas cooled and the resulting solution fractionally distilled. The solereaction product was triethylamine obtained at a conversion of 45%. Thecomplex catalyst remained in solution throughout the hydrogenation.

EXAMPLE 26 A hydrogenation of benzonitrile to dibenzylarnine was carriedout under the same general conditions described in Example 25. However,the nitrile reactant was first diluted with an equal volume of isopropylether, and (C6H5CN)3M0(CO)3 (the benzonitrile-molybdenum carbonylcomplex described in Example 5) was used as the catalyst. The solereaction product was dibenzylarnine obtained at a conversion of 58%. Thecomplex catalyst The complexes of this invention can be characterized bythe general formula where R, M, x, n, y and z are as previously defined.The relative values of n, x, y and z may vary considerably according tothe nature of the nitrile employed in making the complex. Where, forinstance, the nitrile is a saturated mononitrile, x and z are 1 and thesum of n and y is 6. Acetylenically unsaturated mononitriles behavesimilarly.

In the case of a dinitrile, x is, of course, 2 and the relative valuesof x, n, y and z are such that there is a total of at least 6 nitrileand carbonyl groups combined for each atom of metal. Thus, complexeshaving the respective general formulae (NCRCN) M CO) (Example 6) and canbe made from dinitriles, the first formula representing the type ofcomplex obtained when an excess of dinitrile is used as a reactant andthe second formula representing the type obtained when an excess ofmetal carbonyl is employed.

In the preceding instances, the coordinate bonds are between the metaland the nitrile and carbonyl groups.

Olefinic nitriles, on the other hand, react with group VI-B metalcarbonyls to form complexes in which each mole of nitrile replaces twocarbonyl groups. The ostensible reason for this is that both the nitrilegroup and the olefinic bond are involved in the complex (see Example11). In any event, in such complexes the total of nitrile groups,carbonyl groups and olefinic bonds is 6 per atom of metal.

In accordance with this invention, the nitrile-metal carbonyl complexescan be prepared of any nitrile-substituted hydrocarbon or of anitrile-substituted hydrocarbon that contains a nucleophilic group,i.e., a group that increases the electron availability in the triplebond region of the nitrile group. Electrophilic groups, i.e., electronwithdrawing groups, tend to decrease the ability of the nitrile to formthese complexes. Thus, while alkyl, alkoxy and chloro-substituted arylnitriles readily form these new complexes, nitro-substituted arylnitrilesthe nitriles of which the new nitrile-metal carbonyl complexesof this invention can be prepared are nitrilesubstituted hydrocarbonssuch as acetonitrile, propionitrile, n butyronitrile, isobutyronitrile,n-valeronitrile, succinonitrile, adiponitrile, n-capronitrile,acrylonitrile, 3- butenenitrile, propiolonitrile, benzonitrile,p-toluonitrile, phenylacetonitrile, naphthonitrile, etc.;nitrile-substituted oxyhydrocarbons such as 3-hydroxy-butyronitrile,pmethoxy-benzonitrile, etc.; nitrile-substituted amides such ascyanoacetamide, etc.; nitrile-substituted esters such asethylcyanoacetate, etc.; and halo-substituted aromatic nitriles such asp-chlorobenzonitrile, etc.

As demonstrated in the examples, the new nitrilemetal carbonyl complexesof this invention are prepared by either of two methods.

(A) The direct reaction of a nitrile with a group VI-B metal carbonyl.

(B) The displacement of a nitrile from a preformed nitrile-metalcarbonyl complex with another nitrile.

A. Direct Met od Metal carbony-ls of the group VI-B metals, i.e.,molybdenum carbonyl, chromium carbonyl and tungsten carbonyl react withany of the nitriles defined above.

As shown in the examples, this reaction can be carried out in an inertliquid diluent or merely in an excess of the nitrile reactant. Thelatter procedure is preferable in case of liquid, high boiling nitrilesbecause the complexes of this invention are soluble in nitriles but notin most other diluents. However, an inert diluent can be employed if thereaction is conducted at reflux temperature and the nitrile reactantwould decompose the complex sought. Exemplary of inert diluents whichcan be employed are hydrocarbons such as n-heptane, nhexane, n-octane,cyclohexane, etc., ethers such as diisopropyl ether, dipropyl ether,diisobutyl ether, etc., and alcohols such as methanol, ethanol,isopropyl alcohol, etc.

The reaction between a nitrile and a group VlB metal carbonyl is anequilibrium which is normally to the left but can be shifted in thedirection of the formation of the complex by removal of carbon monoxide.Therefore, since the method of this invention is reversible, i.e. caneasily be stopped or reversed by a small partial pressure of carbonmonoxide, it must of necessity be conducted under conditions in whichcarbon monoxide is removed.

The reaction between the nitrile and the metal carbonyl is generallycarried out by heating a mixture of the reactants to a temperature offrom about 40 C. to about 140 C. at or about atmospheric pressure, whileremoving the by-product carbon monoxide as it is formed. Lowertemperatures may be used but generally are not practical, unless theprocess is operated at reduced pressure, due to the slowness of thereaction at such temperatures. One of the simplest methods of carryingout the reaction is by refluxing the reaction mixture at atmospheric ornear atmospheric pressure, whereby the carbon monoxide is removed as itis formed. Refluxing can be conducted over a range of temperatures up toabout 140 C., at which temperature the complexes begin to decompose. Therefluxing period will vary with various reactants, the temperature ofthe reflux, etc., but a sufficient period of time is readilyascertainable since the progress of the reaction is indicated by theamount of carbon monoxide evolved. Another method of conducting thereaction while removing carbon monoxide is by sparging the reactionmixture with an inert gas such as nitrogen.

Recovery of the nitrile-metal carbonyl complex from the reaction mediumcan be accomplished in a number of ways but because of its sensitivityto oxygen, the recovery must be carried out in the absence of air.

The number of nitrile molecules which appear in the final complexdepends primarily upon the ratio of nitrile reactant to metal carbonyl.The number of metal carbonyl groups which appear in the final carbonylcomplex 3 depends upon the number of CN groups present on each nitrilecompound since a mononitrile does not form a complex with more than onemetal carbonyl. However, the ratio of dinitrile to metal carbonyl in thereaction mixture will eifect the number of metal carbonyl groupsappearing in the complex as shown in Examples 6 and 7.

B. Displacement 0r Indirect Method The group or groups comprising thenitrile component of the nitrile-metal carbonyl complex of thisinvention can be displaced by another nitrile compound or compounds asshown in the equation where R, R, M, x, n, y and z are the same asdefined above.

This reaction is also an equilibrium but can be forced to the right byeither adding an excess of the R(CN) or removing the R(CN) in caseswhere the latter is the more volatile nitrile, or by both means. Forexample, when a low boiling nitrile is displaced, such as acetonitrile,the reaction can be forced to completion by evaporation or distillingthe lower boiling nitrile.

The displacement method of this invention can be conducted, in an inertdiluent or in an excess of R(CN) the nitrile reactant. The same inertsolvents can be employed in this method as were employed in the directmethod. Any reaction temperature below the lower of (l) thedecomposition temperature of the complex being formed and (2) thedecomposition temperature of the complex from which it is being formedcan be used in this method. In general, the reaction will be carried outat a temperature below C. Both the reaction and the recovery of thecomplex product are preferably carried out in the absence of air becauseof the sensitivity of the complex.

Exemplary of some of the nitrile-metal carbonyl complexes that can beprepared by this method of the invention are acetonitrile-molybdenumcarbonyl, propionitrilemolybdenum carbonyl, isobutyronitrile-chromiumcarbonyl, benZonitrile-molybdenum carbonyl, benzonitriletungstencarbonyl, succinonitrile-molybdenum carbonyl, malouonitrile-molybdenumcarbonyl, etc.

The method used in the preparation of a desired complex depends on theproperties of the specific reactants and the specific complex desired.While many of the nitrile-metal carbonyl complexes of this invention caneasily be prepared by the direct method, others are more readilyprepared by displacing the nitrile of an easily prepared complex.

There are, of course, still other indirect methods of preparing thecomplexes of this invention such as the displacement of an aromaticcomponent of an aromaticmetal carbonyl complex with a nitrile or thedisplacement of an amine component of an amine-metal carbonyl complexwith a nitrile. For example, either mesitylenemolybdenum tricarbonylcomplex, pyridine-molybdenum tricarbonyl complex orn-butylamine-molybdenum tricarbonyl complex when treated with an excessof acetonitrile, yield the acetonitrile-molybdenum tricarbonyl complexof this invention.

The nitrile-metal carbonyl complexes of this invention are yellow toorange crystalline solids at room temperature which decompose onexposure to air, and exhibit distinctive infrared spectra. In general,they are soluble in most nitriles and to some extent in methanol,ethanol, tetrahydrofuran and the various glycol ethers but areessentially insoluble in other common solvents.

The complexes of this invention possess a variety of uses. They can, forexample, be used for the homogeneous catalytic hydrogenation of nitrilesto secondary or tertiary amines. By homogeneous hydrogenation is meantthe catalyst is completely soluble in the reaction medium and stays insolution during the whole reaction.

Another example of the use of the complexes of this invention ascatalysts is in the field of polymerization such as the polymerizationof butadiene. Still another use is in the condensation of acetaldehydeand acetylene derivatives.

What I claim and desire to protect by Letters Patent is:

1. A crystalline complex of a nitrile and a group VI-B metal carbonyl,said complex having the general formula in which R is a nucleophilicgroup selected from the class consisting of hydrocarbon groups,oxyhydrocarbon groups, alkoxyhydrocarbon groups, aliphatic amide groups,aliphatic ester groups, and halo-substituted aromatic hydrocarbongroups, M is a hexacoordinated metal of group VI-B of the periodictable, x is an integer from 1 to 2 inclusive, n is an integer from 1 to3 inclusive, y is an integer from 2 to 5 inclusive and z is an integerfrom 1 to 2 inclusive, wherein x, n, y and z have one of therelationships selected from (a) x and z are each 1 and the sum of n+y is6, (b) x and z are each 1 and the sum of n-l-y is 4 (c) x is 2, z is 1and the sum of n+y is 6, and (d) x and z are each 2 and the sum of n+yis 6.

2. The complex of claim 1 wherein the metal is chromium.

3. The complex of claim "1 wherein the metal is molybdenum.

4. The complex of claim 1 wherein the sten.

5. The complex of claim 1 wherein the nitrile is an aliphatichydrocarbon nitrile.

6. The complex of claim 1 wherein the nitrile is an aromatic hydrocarbonnitrile.

7. The complex of claim 1 wherein the nitrile is an alkoxy-substitutedaromatic hydrocarbon nitrile.

8. The complex of claim 1 wherein the nitrile is a chloro-substitutedaromatic hydrocarbon nitrile.

9. The complex of claim 5 wherein the nitrile is acetonitrile.

10. An acetonitrile-molybdenum carbonyl complex having the formula(CH3CN)3MO(CO)3.

11. A benzonitrile molybdenum carbonyl complex having the formula (C HCN) M(CO) 12. An adiponitrile-molybdenum carbonyl complex having theformula [NC(CH CN] M0 (CO) 13. A propionitrile-molybdenum carbonylcomplex having the formula (C H CN) Mo (CO).;.

14. Acrylonitrile-molybdenum carbonyl complex having the formula(CI-IFCHCN) Mo(CO) 15 The method of preparing a crystalline complex of anitrile and a group VI-B metal which comprises reacting a metal carbonylhaving the formula M(CO) where M is a hexacoordinated metal of groupVI-B of the periodic table with a nitrile having the formula R(CN) whereR is a nucleophilic group selected from the class consisting ofhydrocarbon groups, oxyhydrocarbon groups, alkoxyhydrocarbon groups,aliphatic amide groups, aliphatic ester groups, and halo-substitutedaromatic hydrocarbon groups, and x is an integer from 1 to 2 inclusiveunder conditions where carbon monoxide is removed as it is formed.

metal is tung- 16. The method of claim 15 wherein the metal ismolybdenum. 1

17. The method of claim 15 wherein the nitrile is acetonitrile.

18. The method of claim 15 wherein the nitrile is benzonitrile.

19. The method of claim 15 wherein the nitrile is pro pionitrile.

20. The method of claim 15 wherein the nitrile is adiponitrile.

21. The method of claim 15 wherein the nitrile is acrylonitrile.

22. The method of preparing a crystalline complex of a nitrile and agroup VI-B metal which comprises reacting a nitrile-metal carbonylcomplex having the general formula [R(CN), ],,[M(CO) in which R is anucleophilic group selected from the class consisting of hydrocarbongroups, oxyhydrocarbon groups, alkoxyhydrocarbon groups, aliphatic amidegroups, aliphatic ester groups, and halo-substituted aromatichydrocarbon groups, M is a hexacoordinated metal of group VI-B of theperiodic table, x is an integer from 1 to 2 inclusive, n is an integerfrom 1 to 3 inclusive, y is an integer from 2 to 5 inclusive and z is aninteger from 1 to 2 inclusive with a different nitrile from the nitrilecomponent of said nitrilernetal carbonyl complex, said difierent nitrilehaving the formula R(CN) where R is a nucleophilic group selected fromthe class consisting of hydrocarbon groups, oxyhydrocarbon groups,alkoxyhydrocarbon groups, aliphatic amide groups, aliphatic estergroups, and halo-substituted aromatic hydrocarbon groups, R being adiiferent substituent group from R and x is an integer from 1 to 2inclusive, thereby replacing the nitrile component of the complex withanother nitrile component, x, n, y and z in said formula having one ofthe relationships selected from (a) x and z are each 1 and the sum ofn+y is 6, (b) x and z are each 1 and the sum of n+y is 4, (c) x is 2, zis 1 and the sum of n+y is 6, and (d) x and z are each 2 and the sum ofn-l-y is 6.

23. The method of claim 22 wherein said nitrile-metal carbonyl complexis an acetonitrile-molybdenum carbonyl complex.

24. The method of claim 23 wherein said different nitrile isbenzonitrile.

25. The method of claim 23 wherein said difierent nitrile iscapronitrile.

26. The method of claim 23 wherein said different nitrile ismalononitrile.

References Cited in the file of this patent Natta et al.: La Ohimica ELlndustria, vol. 40, No. 12, pp. 10034007, 1958.

Wertheim: Organic Chemistry, third edition, McGraw Hill Book Co., Inc.(1951), p. 327 relied on.

Klages et al.: Chemische Berichte, vol. 83, No. 6, October 1950, pp.501-508 relied on.

Hieber et al.: Chemische Berichte, vol. 89, No. 3, March 1956, pp.616-619 relied on.

Huber: Uber Neue, nicht-Salzartige, Komplexe des Molybdan (XI p. 32relied on.

1. A CRYSTALLINE COMPLEX OF A NITRILE AND A GROUP VI-B METAL CARBONYL,SAID COMPLEX HAVING THE GENERAL FORMULA